Analysis And Design Of Internal Measuring Claw Device Applied To General Calipers

Metrology is a science of measurement,a science of practice,and an activity to realize the unity of measurement units and accurate and reliable measurement values;it is also an important basis for economic construction,national defense construction,scientific research and social development of all countries in the world.General calipers play an important role in length measurement and are widely used in traditional industrial fields such as machinery manufacturing,steel industry,textile industry,leather industry,etc.the accuracy of measurement is the guarantee of the quality of parts.In recent decades,with the rapid development of Electronic Science and technology,universal calipers are also widely used in the preparation and detection of electronic devices such as capacitors,inductors and resistors.The internal measuring claw of universal caliper is one of the main structures of universal caliper,and its indication error directly affects the accuracy of measurement value.In 2012,the verification regulation of general calipers puts forward new requirements for indication error of internal measuring claw.However,the special inspection tools for internal dimension,such as smooth ring gauge and step gauge,are recommended to be used in the verification regulation.The indication value is single,and there is no sufficient specification for verification and calibration.With the increase of nominal value,the volume and weight of ring gauge and step gauge with different specifications increase It is difficult to use,carry and keep,so it is not suitable for verification and calibration.However,the universal length measuring instrument with special internal dimension measuring tool and fixed standard gauge block can only measure the internal measuring claw size within the scope of 300 mm.In recent years,in the process of mechanical manufacturing,automatic design and electronic device production,the universal calipers larger than 300 mm have been widely used,and the existing internal measuring claw verification device can no longer meet the needs of relevant industries.This paper introduces the internal measuring claw of universal calipers at home and abroad as well as the related theoretical knowledge.In view of the shortcomings of the existing internal measuring claw,combined with the structural characteristics of the universal caliper standard gauge block,the length,material,structure and other aspects of the inspection fixture are improved,and the measuring device is upgraded,and the measurement method of direct reading is proposed.The reliability and convenience of the designed verification device for the internal measuring claw of the general calipers are proved by several design upgrades of the verification device,combined with the uncertainty evaluation of the universal caliper and the comparison between laboratories.